Nest‐site selection exerts a fundamental maternal effect on offspring fitness in oviparous species. In many freshwater turtles, females do not care for their eggs after oviposition but rather rely on a nest's micro‐environment to incubate developing embryos although linkages between oviposition choices and overall fitness remain poorly evaluated. We tested predictions derived from multiple hypotheses to examine nesting patterns of the yellow‐spotted river turtle Podocnemis unifilis, a species imperiled by egg harvesting by humans throughout its range, based on data collected from 73 nesting sites along 118 km of river in the eastern Brazilian Amazon. Nesting area size largely explained nest‐site selection by turtles, but only weakly explained turtle egg harvesting by humans. Despite the wide availability of alternative nesting habitats, turtles do not appear to be capable of avoiding hazardous nesting sites associated with increased egg harvesting by humans. Because signals used by female turtles to select nesting areas are apparently not sufficient for avoiding nesting along rivers accessible to humans, direct conservation action will be vital for persistence of these and likely other Amazonian freshwater turtles.

Substrate type determines nesting success and fitness in turtles and is a critical consideration for nesting area protection and restoration. Here, we evaluated the effect of substrate on nest removal by humans in the eastern Brazilian Amazon. We analyzed substrate composition and fate of 216 P. unifilis nests along 88 km of rivers. River segment and substrate type were the most important predictors of nest removal by humans. We found up to 36% lower removal of nests in fine sand and experimental results support the hypothesis that wind more often obscures tracks of nesting females in substrates with more (>66%) fine sand. Our findings are useful for informing the restoration of artificial nesting areas across the Amazon, as nesting area substrates should be selected not only to maintain hatchling sex ratios, but also to minimize nest removal by humans. Turtles are experiencing global population declines 1 , with approximately 61% of all species threatened with extinction or already extinct 2. This issue is particularly acute in the tropics, where turtles represent food and income for local populations 1,3-5. Survival of exploited turtle populations can be enhanced by habitat restoration 6-8. For example, increasing available nesting habitat improved population growth in threatened marine turtles 9,10 and recruitment in temperate freshwater turtles 11,12. In contrast, the restoration of terrestrial nesting habitats for tropical freshwater turtles remains poorly explored. The Amazon basin encapsulates 21 st century conservation challenges for tropical freshwater turtles. Myriad threats to species and populations mean that the priorities for freshwater turtle conservation actions remain intensely debated 13. Among the factors affecting long-term turtle population viability, adult survival has been demonstrated to be crucial 14,15 , but nest-site selection by female turtles is also a key process for reproductive success and maternal survival 16-18. The once common freshwater turtles (Podocnemis spp.) are declining across Amazonia due to rampant overexploitation of both adults and eggs 19,20 , and the loss and degradation of aquatic (feeding, dispersal and reproduction) and terrestrial (nesting) habitat due to deforestation 21 and hydroelectric expansion 19. Additionally, as with many wildlife species across Amazonia, the lack of effective enforcement of existing regulations 22,23 and ineffective environmental impact assessments 22,24,25 mean that conservation actions have failed to generate widespread recoveries 5,26. Currently, the yellow-spotted river turtle (Podocnemis unifilis) is classified as Vulnerable (A1acd) by the IUCN 27 , with a recommended revision to Endangered 5. P. unifilis is a widespread freshwater species found across the Amazon, North Atlantic and Orinoco river basins 27,28. This is a relatively large species (females can weight up to 12 kg) that has been exploited since the pre-colonial period (pre 18th century) and is still widely consumed by indigenous and riverine peoples across Amazonia 4,20...